In Layer 2 switched networks, network administrators are well aware of the downside of network loops and therefore are extremely cautious in provisioning loop prevention techniques. Some example loop prevention techniques include ITU-T Recommendation G.8032/Y.1344 (08/15) “Ethernet Ring Protection Switching,” IEEE 802.1ad Spanning Tree Protocol (xSTP may generically refer to a Spanning Tree Protocol, including any one of standard Spanning Tree Protocol (STP), Rapid Spanning Tree Protocol (RSTP), Multiple Spanning Tree Protocol (MSTP), or variations thereof), etc. Despite the use of loop prevention techniques, inadvertent loops may still form due to network runtime changes such as for debugging or scaling reasons; customer network loops sometimes create unintentional loops, etc. There are existing techniques to detect loops that occur in connected customer networks, and, once detected, these techniques report an alarm and/or block the specific service from entering the network, or, in worst cases, simply force down the customer port where the specific service is entering the network. However, there is no known mechanism and action which consistently works to safeguard a provider network from its own as well as customer network loops.
Known loop prevention actions configured by service providers primarily address issues caused by customer network loops by applying certain actions on User-Network Interface (UNI) ports. A “Port shutdown” (i.e., force operational down) action can be applied on UNIs only and would disrupt all traffic on that UNI. Service based actions such as an STP block needs to be enabled per service. The service, on which this action is applied, will drop all frames of the problematic service (even if the problem is limited to certain flows such as Source Media Access Control (MAC) addresses). Additionally, with this action enable, a user cannot determine whether the loop condition has been resolved. This capability is extremely important if customer network loops are transient and correct within a short duration.